Newly walking toddlers face difficult challenges in learning to walk. Such challenges result from the high number of degrees-of-freedom of individual body segment rotations and the inherent variability of body motion during bipedal gait in a gravitational field.
In learning to walk, toddlers may take up to 9000 steps per day. For the average toddler, this is equivalent to traversing the length of more than 20 football fields. During these first steps, and throughout the learning process, newly walking toddlers may be assisted in their exploratory behavior by adults who stabilize their body motion by holding one or both hands, or supporting the toddler's trunk at the hips. Adults assisting toddlers learning to walk provide ever-changing postural support that provides the toddlers the opportunity to safely explore the forces acting on their bodies.
A fundamental challenge in learning to walk is that stepping attempts result in simultaneous body motion in two planes, anterior-posterior and medial-lateral. However, with an abundance of body degrees-of-freedom (DOF) to control, toddlers appear to be able to learn to control body motion in only one plane at a time. As most toddlers learn to walk, the toddlers learn to reduce variability in one plane of motion while relaxing motion variability in another other. However, there are limits to the toddlers' abilities to use their muscles to control motion variability. Therefore, learning may be a continuously modulated process, rather than a fixed or absolute freezing in one plane and relaxation in the other.
Adding to the complexity and challenges in learning to walk for some toddlers can be developmental delays caused by injury (e.g., brain injury or other bodily injury). Premature birth remains a major public health problem despite recent advances. By way of example, in 2008 alone, 1.5% of the more than 4.25 million births (i.e., more than 63,000 infants) were born at a very low birth weight (VLBW) (≤1500 g). Of the 90% of surviving VLBW infants, 25-50% experienced a brain injury that accounts for delays in locomotive development. The long-term consequences of early brain injury (e.g., in children born prematurely) constitute a major health problem and a significant emotional and financial burden for families and society.
Therefore, a need exists for developing locomotive motion in developmentally-delayed toddlers to relieve the physical, emotional and financial burdens such development delay causes.